Optimization of a Binary Concrete Crack Self-Healing System Containing Bacteria and Oxygen

An optimized strategy for the enhancement of microbially induced calcium precipitation including spore viability ensurance, nutrient selection and O(2) supply was developed. Firstly, an optimal yeast extract concentration of 5 g/L in sporulation medium was determined based on viable spore yield and spore viability. Furthermore, the effects of certain influential factors on microbial calcium precipitation process of H4 in the presence of oxygen releasing tablet (ORT) were evaluated. The results showed that CaO(2) is preferable to other peroxides in improving the calcium precipitation by H4. H4 strain is able to precipitate a highly insoluble calcium at the CaO(2) dosage range of 7.5–12.5 g/L, and the most suitable spore concentration is 6 × 10(8) spores/ml when the spore viability (viable spore ratio) is approximately 50%. Lactate is the best carbon source and nitrate is the best nitrogen source for aerobic incubation. This work has laid a foundation of ternary self-healing system containing bacteria, ORT, and nutrients, which will be promising for the self-healing of cracks deep inside the concrete structure.